This invention relates to a metal gasket for use in automobile engines, screw engines, freezing equipment, air conditioning units and the like and a method of producing the metal gasket.
As gaskets for automobile engines, so-called asbestos type gaskets have been widely used which are made of single, jointed or beat sheets of asbestos as sole or composite materials. Recently, however, various kinds of new type gaskets have been progressively practically used which are made of metals, graphites, fibers and the like as sole or composite materials in place of the asbestos causing a problem of public nuisance. Particularly, metal gaskets provided on their surfaces with rubber layers are superior in performance and cost to other new gaskets in substitution for the asbestos gaskets and expected to be widely used in future.
Sealing faculty and durability are important among various faculties required as gaskets for automobiles. It has been proposed to deposit a rubber coating layer directly on surfaces of a metal plate as a substrate in order to improve the sealing faculty. In case of metal gaskets, however, the sealing faculty and durability depend mainly upon bonding power between the metal plate and the rubber coating layer. It is therefore important in manufacturing the rubber coated metal gaskets to improve the bonding power therebetween and to prevent the bonding power from lowering in used conditions.
Therefore, attempt has been made to improve the bonding power between the metal plate and the bonding layer or the rubber layer and to maintain the improved bonding power for a long period of time with the aid of an activation treatment or galvanizing which is applied to the surfaces of the metal plate.
Recently, however, high performance automobile engines have been developed and widely used so that metal gaskets are also used under severer conditions, with the result that the durability of the gaskets becomes more important. Under such circumstances, even the above gaskets of metals coated with rubber coating layers encounter a problem of insufficient durability.